| 摘要 |
PROBLEM TO BE SOLVED: To stably discharge curled chips and provide good chip discharging performance by forming a breaker groove immediately after the nose tip of a cutting insert to be recessed with respect to both side parts and specifying the rake angle or the like of a side cutting edge. SOLUTION: A cutting insert 10 is formed in a rhombic shape where the included angle of a nose part 4 is relatively larger, and a cutting edge 3 composed of a tip cutting edge 3a and a side cutting edge 3b is formed in an edge side between a face 1 and a flank 2. A breaker groove 6 is formed in the nose part 4 to be continuous from the cutting edge 3, and a breaker projection 8 is formed in the center part of the breaker groove 6. In this case, the breaker groove 6 is formed to be recessed with respect to both side parts. Then, the rake angle (α) of the side cutting edge 3b is set equal to 5 deg. or more, and the side cutting edge 3b is set to have a down angleβ=4 deg. to 8 deg. in the direction of being shifted from the nose tip. Thus, chip resistance in the nose tip is reduced, and chips are surely curled.
|
